Semiconductor device and method of forming openings through insulating layer over encapsulant for enhanced adhesion of interconnect structure

ABSTRACT

A semiconductor device has a semiconductor die mounted to a carrier. An encapsulant is deposited over the semiconductor die and carrier. The carrier is removed. A first insulating layer is formed over a portion of the encapsulant within an interconnect site outside a footprint of the semiconductor die. An opening is formed through the first insulating layer within the interconnect site to expose the encapsulant. The opening can be ring-shaped or vias around the interconnect site and within a central region of the interconnect site to expose the encapsulant. A first conductive layer is formed over the first insulating layer to follow a contour of the first insulating layer. A second conductive layer is formed over the first conductive layer and exposed encapsulant. A second insulating layer is formed over the second conductive layer. A bump is formed over the second conductive layer in the interconnect site.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device and method of forming anopening through an insulating layer over an encapsulant for enhancedadhesion of an interconnect structure.

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products.Semiconductor devices vary in the number and density of electricalcomponents. Discrete semiconductor devices generally contain one type ofelectrical component, e.g., light emitting diode (LED), small signaltransistor, resistor, capacitor, inductor, and power metal oxidesemiconductor field effect transistor (MOSFET). Integrated semiconductordevices typically contain hundreds to millions of electrical components.Examples of integrated semiconductor devices include microcontrollers,microprocessors, charged-coupled devices (CCDs), solar cells, anddigital micro-mirror devices (DMDs).

Semiconductor devices perform a wide range of functions such as signalprocessing, high-speed calculations, transmitting and receivingelectromagnetic signals, controlling electronic devices, transformingsunlight to electricity, and creating visual projections for televisiondisplays. Semiconductor devices are found in the fields ofentertainment, communications, power conversion, networks, computers,and consumer products. Semiconductor devices are also found in militaryapplications, aviation, automotive, industrial controllers, and officeequipment.

Semiconductor devices exploit the electrical properties of semiconductormaterials. The atomic structure of semiconductor material allows itselectrical conductivity to be manipulated by the application of anelectric field or base current or through the process of doping. Dopingintroduces impurities into the semiconductor material to manipulate andcontrol the conductivity of the semiconductor device.

A semiconductor device contains active and passive electricalstructures. Active structures, including bipolar and field effecttransistors, control the flow of electrical current. By varying levelsof doping and application of an electric field or base current, thetransistor either promotes or restricts the flow of electrical current.Passive structures, including resistors, capacitors, and inductors,create a relationship between voltage and current necessary to perform avariety of electrical functions. The passive and active structures areelectrically connected to form circuits, which enable the semiconductordevice to perform high-speed calculations and other useful functions.

Semiconductor devices are generally manufactured using two complexmanufacturing processes, i.e., front-end manufacturing, and back-endmanufacturing, each involving potentially hundreds of steps. Front-endmanufacturing involves the formation of a plurality of die on thesurface of a semiconductor wafer. Each die is typically identical andcontains circuits formed by electrically connecting active and passivecomponents. Back-end manufacturing involves singulating individual diefrom the finished wafer and packaging the die to provide structuralsupport and environmental isolation.

One goal of semiconductor manufacturing is to produce smallersemiconductor devices. Smaller devices typically consume less power,have higher performance, and can be produced more efficiently. Inaddition, smaller semiconductor devices have a smaller footprint, whichis desirable for smaller end products. A smaller die size may beachieved by improvements in the front-end process resulting in die withsmaller, higher density active and passive components. Back-endprocesses may result in semiconductor device packages with a smallerfootprint by improvements in electrical interconnection and packagingmaterials.

In a fan-out wafer level chip scale package (Fo-WLCSP), a semiconductordie has an active surface containing analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed within the die and electrically interconnectedaccording to the electrical design and function of the die. Anencapsulant is deposited over the semiconductor die. A first passivationlayer is formed over encapsulant. A redistribution layer (RDL) is formedover first passivation layer. A second passivation layer is formed overthe RDL and first passivation layer. A portion of the second passivationlayer is removed by an etching process to expose RDL. Bumps are formedover the RDL in the removed portions of the second passivation layer.

The adhesion between the first passivation and encapsulant tends to beweak in many Fo-WLCSPs. The weak adhesion between the first passivationand encapsulant is particularly apparent during reliability test, e.g.,drop test. The device can be rejected by post-reliability inspection, orthe device could fail in the field.

SUMMARY OF THE INVENTION

A need exists to reduce failure of bump structures on semiconductordevices. Accordingly, in one embodiment, the present invention is amethod of making a semiconductor device comprising the steps ofproviding a carrier, mounting a semiconductor die to the carrier,depositing an encapsulant over the semiconductor die and carrier,removing the carrier, forming a first insulating layer over a portion ofthe encapsulant within an interconnect site outside a footprint of thesemiconductor die, removing a portion of the first insulating layerwithin the interconnect site to expose the encapsulant, forming a firstconductive layer over the first insulating layer and exposedencapsulant, forming a second insulating layer over the first conductivelayer, and forming a bump over the first conductive layer in theinterconnect site.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a carrier,mounting a semiconductor die to the carrier, depositing an encapsulantover the semiconductor die and carrier, removing the carrier, forming afirst insulating layer over a portion of the encapsulant within aninterconnect site outside a footprint of the semiconductor die, formingan opening through the first insulating layer within the interconnectsite to expose the encapsulant, and forming a first conductive layerover the first insulating layer and exposed encapsulant.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a semiconductordie, depositing an encapsulant over and around the semiconductor die,forming a first insulating layer over a portion of the encapsulantwithin an interconnect site outside a footprint of the semiconductordie, forming an opening through the first insulating layer within theinterconnect site to expose the encapsulant, and forming a firstconductive layer over the first insulating layer and exposedencapsulant.

In another embodiment, the present invention is a semiconductor devicecomprising a semiconductor die and encapsulant deposited over and aroundthe semiconductor die. A first insulating layer is formed over a portionof the encapsulant within an interconnect site outside a footprint ofthe semiconductor die. An opening is formed through the first insulatinglayer within the interconnect site to expose the encapsulant. A firstconductive layer is formed over the first insulating layer and exposedencapsulant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional bump structure formed over asemiconductor wafer;

FIGS. 2a-2c illustrate a PCB with different types of packages mounted toits surface;

FIGS. 3a-3c illustrate further detail of the representativesemiconductor packages mounted to the PCB;

FIGS. 4a-4k illustrate a process of forming openings through aninsulating layer over an encapsulant for enhanced adhesion of aninterconnect structure; and

FIGS. 5a-5e illustrate another process of forming openings through aninsulating layer over an encapsulant for enhanced adhesion of aninterconnect structure.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings.

Semiconductor devices are generally manufactured using two complexmanufacturing processes: front-end manufacturing and back-endmanufacturing. Front-end manufacturing involves the formation of aplurality of die on the surface of a semiconductor wafer. Each die onthe wafer contains active and passive electrical components, which areelectrically connected to form functional electrical circuits. Activeelectrical components, such as transistors and diodes, have the abilityto control the flow of electrical current. Passive electricalcomponents, such as capacitors, inductors, resistors, and transformers,create a relationship between voltage and current necessary to performelectrical circuit functions.

Passive and active components are formed over the surface of thesemiconductor wafer by a series of process steps including doping,deposition, photolithography, etching, and planarization. Dopingintroduces impurities into the semiconductor material by techniques suchas ion implantation or thermal diffusion. The doping process modifiesthe electrical conductivity of semiconductor material in active devices,transforming the semiconductor material into an insulator, conductor, ordynamically changing the semiconductor material conductivity in responseto an electric field or base current. Transistors contain regions ofvarying types and degrees of doping arranged as necessary to enable thetransistor to promote or restrict the flow of electrical current uponthe application of the electric field or base current.

Active and passive components are formed by layers of materials withdifferent electrical properties. The layers can be formed by a varietyof deposition techniques determined in part by the type of materialbeing deposited. For example, thin film deposition may involve chemicalvapor deposition (CVD), physical vapor deposition (PVD), electrolyticplating, and electroless plating processes. Each layer is generallypatterned to form portions of active components, passive components, orelectrical connections between components.

The layers can be patterned using photolithography, which involves thedeposition of light sensitive material, e.g., photoresist, over thelayer to be patterned. A pattern is transferred from a photomask to thephotoresist using light. The portion of the photoresist patternsubjected to light is removed using a solvent, exposing portions of theunderlying layer to be patterned. The remainder of the photoresist isremoved, leaving behind a patterned layer. Alternatively, some types ofmaterials are patterned by directly depositing the material into theareas or voids formed by a previous deposition/etch process usingtechniques such as electroless and electrolytic plating.

Depositing a thin film of material over an existing pattern canexaggerate the underlying pattern and create a non-uniformly flatsurface. A uniformly flat surface is required to produce smaller andmore densely packed active and passive components. Planarization can beused to remove material from the surface of the wafer and produce auniformly flat surface. Planarization involves polishing the surface ofthe wafer with a polishing pad. An abrasive material and corrosivechemical are added to the surface of the wafer during polishing. Thecombined mechanical action of the abrasive and corrosive action of thechemical removes any irregular topography, resulting in a uniformly flatsurface.

Back-end manufacturing refers to cutting or singulating the finishedwafer into the individual die and then packaging the die for structuralsupport and environmental isolation. To singulate the die, the wafer isscored and broken along non-functional regions of the wafer called sawstreets or scribes. The wafer is singulated using a laser cutting toolor saw blade. After singulation, the individual die are mounted to apackage substrate that includes pins or contact pads for interconnectionwith other system components. Contact pads formed over the semiconductordie are then connected to contact pads within the package. Theelectrical connections can be made with solder bumps, stud bumps,conductive paste, or wirebonds. An encapsulant or other molding materialis deposited over the package to provide physical support and electricalisolation. The finished package is then inserted into an electricalsystem and the functionality of the semiconductor device is madeavailable to the other system components.

FIG. 1 illustrates electronic device 50 having a chip carrier substrateor printed circuit board (PCB) 52 with a plurality of semiconductorpackages mounted on its surface. Electronic device 50 may have one typeof semiconductor package, or multiple types of semiconductor packages,depending on the application. The different types of semiconductorpackages are shown in FIG. 1 for purposes of illustration.

Electronic device 50 may be a stand-alone system that uses thesemiconductor packages to perform one or more electrical functions.Alternatively, electronic device 50 may be a subcomponent of a largersystem. For example, electronic device 50 may be part of a cellularphone, personal digital assistant (PDA), digital video camera (DVC), orother electronic communication device. Alternatively, electronic device50 can be a graphics card, network interface card, or other signalprocessing card that can be inserted into a computer. The semiconductorpackage can include microprocessors, memories, application specificintegrated circuits (ASIC), logic circuits, analog circuits, RFcircuits, discrete devices, or other semiconductor die or electricalcomponents. The miniaturization and the weight reduction are essentialfor these products to be accepted by the market. The distance betweensemiconductor devices must be decreased to achieve higher density.

In FIG. 1, PCB 52 provides a general substrate for structural supportand electrical interconnect of the semiconductor packages mounted on thePCB. Conductive signal traces 54 are formed over a surface or withinlayers of PCB 52 using evaporation, electrolytic plating, electrolessplating, screen printing, or other suitable metal deposition process.Signal traces 54 provide for electrical communication between each ofthe semiconductor packages, mounted components, and other externalsystem components. Traces 54 also provide power and ground connectionsto each of the semiconductor packages.

In some embodiments, a semiconductor device has two packaging levels.First level packaging is a technique for mechanically and electricallyattaching the semiconductor die to an intermediate carrier. Second levelpackaging involves mechanically and electrically attaching theintermediate carrier to the PCB. In other embodiments, a semiconductordevice may only have the first level packaging where the die ismechanically and electrically mounted directly to the PCB.

For the purpose of illustration, several types of first level packaging,including wire bond package 56 and flip chip 58, are shown on PCB 52.Additionally, several types of second level packaging, including ballgrid array (BGA) 60, bump chip carrier (BCC) 62, dual in-line package(DIP) 64, land grid array (LGA) 66, multi-chip module (MCM) 68, quadflat non-leaded package (QFN) 70, and quad flat package 72, are shownmounted on PCB 52. Depending upon the system requirements, anycombination of semiconductor packages, configured with any combinationof first and second level packaging styles, as well as other electroniccomponents, can be connected to PCB 52. In some embodiments, electronicdevice 50 includes a single attached semiconductor package, while otherembodiments call for multiple interconnected packages. By combining oneor more semiconductor packages over a single substrate, manufacturerscan incorporate pre-made components into electronic devices and systems.Because the semiconductor packages include sophisticated functionality,electronic devices can be manufactured using cheaper components and astreamlined manufacturing process. The resulting devices are less likelyto fail and less expensive to manufacture resulting in a lower cost forconsumers.

FIGS. 2a-2c show exemplary semiconductor packages. FIG. 2a illustratesfurther detail of DIP 64 mounted on PCB 52. Semiconductor die 74includes an active region containing analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed within the die and are electricallyinterconnected according to the electrical design of the die. Forexample, the circuit may include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements formedwithin the active region of semiconductor die 74. Contact pads 76 areone or more layers of conductive material, such as aluminum (Al), copper(Cu), tin (Sn), nickel (Ni), gold (Au), or silver (Ag), and areelectrically connected to the circuit elements formed withinsemiconductor die 74. During assembly of DIP 64, semiconductor die 74 ismounted to an intermediate carrier 78 using a gold-silicon eutecticlayer or adhesive material such as thermal epoxy or epoxy resin. Thepackage body includes an insulative packaging material such as polymeror ceramic. Conductor leads 80 and wire bonds 82 provide electricalinterconnect between semiconductor die 74 and PCB 52. Encapsulant 84 isdeposited over the package for environmental protection by preventingmoisture and particles from entering the package and contaminating die74 or wire bonds 82.

FIG. 2b illustrates further detail of BCC 62 mounted on PCB 52.Semiconductor die 88 is mounted over carrier 90 using an underfill orepoxy-resin adhesive material 92. Wire bonds 94 provide first levelpackaging interconnect between contact pads 96 and 98. Molding compoundor encapsulant 100 is deposited over semiconductor die 88 and wire bonds94 to provide physical support and electrical isolation for the device.Contact pads 102 are formed over a surface of PCB 52 using a suitablemetal deposition process such as electrolytic plating or electrolessplating to prevent oxidation. Contact pads 102 are electricallyconnected to one or more conductive signal traces 54 in PCB 52. Bumps104 are formed between contact pads 98 of BCC 62 and contact pads 102 ofPCB 52.

In FIG. 2c , semiconductor die 58 is mounted face down to intermediatecarrier 106 with a flip chip style first level packaging. Active region108 of semiconductor die 58 contains analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed according to the electrical design of the die.For example, the circuit may include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements withinactive region 108. Semiconductor die 58 is electrically and mechanicallyconnected to carrier 106 through bumps 110.

BGA 60 is electrically and mechanically connected to PCB 52 with a BGAstyle second level packaging using bumps 112. Semiconductor die 58 iselectrically connected to conductive signal traces 54 in PCB 52 throughbumps 110, signal lines 114, and bumps 112. A molding compound orencapsulant 116 is deposited over semiconductor die 58 and carrier 106to provide physical support and electrical isolation for the device. Theflip chip semiconductor device provides a short electrical conductionpath from the active devices on semiconductor die 58 to conductiontracks on PCB 52 in order to reduce signal propagation distance, lowercapacitance, and improve overall circuit performance. In anotherembodiment, the semiconductor die 58 can be mechanically andelectrically connected directly to PCB 52 using flip chip style firstlevel packaging without intermediate carrier 106.

FIG. 3a shows a semiconductor wafer 120 with a base substrate material122, such as silicon, germanium, gallium arsenide, indium phosphide, orsilicon carbide, for structural support. A plurality of semiconductordie or components 124 is formed on wafer 120 separated by saw streets126 as described above.

FIG. 3b shows a cross-sectional view of a portion of semiconductor wafer120. Each semiconductor die 124 has a back surface 128 and activesurface 130 containing analog or digital circuits implemented as activedevices, passive devices, conductive layers, and dielectric layersformed within the die and electrically interconnected according to theelectrical design and function of the die. For example, the circuit mayinclude one or more transistors, diodes, and other circuit elementsformed within active surface 130 to implement analog circuits or digitalcircuits, such as digital signal processor (DSP), ASIC, memory, or othersignal processing circuit. Semiconductor die 124 may also containintegrated passive devices (IPDs), such as inductors, capacitors, andresistors, for RF signal processing. In one embodiment, semiconductordie 124 is a flipchip type semiconductor die.

An electrically conductive layer 132 is formed over active surface 130using PVD, CVD, electrolytic plating, electroless plating process, orother suitable metal deposition process. Conductive layer 132 can be oneor more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitable electricallyconductive material. Conductive layer 132 operates as contact padselectrically connected to the circuits on active surface 130. Bumps 134are formed on contact pads 132.

An insulating or dielectric layer 136 is formed over active surface 130and conductive layer 132 using PVD, CVD, screen printing, spin coating,spray coating, sintering or thermal oxidation. The insulating layer 136contains one or more layers of silicon dioxide (SiO2), silicon nitride(Si3N4), silicon oxynitride (SiON), tantalum pentoxide (Ta2O5), aluminumoxide (Al2O3), or other material having similar insulating andstructural properties. A portion of insulating layer 136 is removed byan etching process to expose contact pads 132.

In FIG. 3c , semiconductor wafer 120 is singulated through saw street126 using a saw blade or laser cutting tool 138 into individualsemiconductor die 124.

FIGS. 4a-4k illustrate, in relation to FIGS. 1 and 2 a-2 c, a process offorming an opening through an insulating layer over an encapsulant forenhanced adhesion of an interconnect structure. FIG. 4a shows asubstrate or carrier 140 containing temporary or sacrificial basematerial such as silicon, polymer, beryllium oxide, or other suitablelow-cost, rigid material for structural support. An interface layer ordouble-sided tape 142 is formed over carrier 140 as a temporary adhesivebonding film or etch-stop layer.

Semiconductor die 124 from FIGS. 3a-3c is positioned over and mounted tocarrier 140 using a pick and place operation with insulating layer 136oriented toward the carrier. FIG. 4b shows semiconductor die 124 mountedto carrier 140 with insulating layer 136 and contact pads 132 abuttinginterface layer 142.

In FIG. 4c , an encapsulant or molding compound 144 is deposited oversemiconductor die 124 and interface layer 142 using a paste printing,compressive molding, transfer molding, liquid encapsulant molding,vacuum lamination, spin coating, or other suitable applicator.Encapsulant 144 can be polymer composite material, such as epoxy resinwith filler, epoxy acrylate with filler, or polymer with proper filler.Encapsulant 144 is non-conductive and environmentally protects thesemiconductor device from external elements and contaminants.

In FIG. 4d , carrier 140 and interface layer 142 are removed by chemicaletching, mechanical peel-off, CMP, mechanical grinding, thermal bake,laser scanning, or wet stripping to expose contact pads 132. Aninsulating or passivation layer 146 is formed over semiconductor die 124and encapsulant 144 using PVD, CVD, screen printing, spin coating, spraycoating, sintering or thermal oxidation. The insulating layer 146contains one or more layers of SiO2, Si3N4, SiON, Ta2O5, Al2O3, or othermaterial having similar insulating and structural properties. A portionof insulating layer 146 is removed by an etching process to form anopening or via 148 and expose contact pads 132 and encapsulant 144.

FIG. 4e shows a plan view of insulating layer 146 and opening 148. Inparticular, opening 148 in insulating layer 146 has a ring shape withininterconnect site or bump formation area 150 to expose encapsulant 144outside a footprint of semiconductor die 124. In one embodiment, thewidth of ring-shaped opening 148 is 20-100 micrometers (μm).

FIG. 4f shows a plan view of another embodiment of insulating layer 146and openings 152 formed as four isolated circles or vias at 90 degreeincrements around interconnect site or bump formation area 153. Theopenings 152 have a similar cross-sectional view as FIG. 4e and exposeencapsulant 144 outside a footprint of semiconductor die 124. Theopenings 152 can be distributed near the edge, e.g., 40 μm clearance, ofinterconnect site 153.

FIG. 4g shows a plan view of another embodiment of insulating layer 146and openings 154 formed as a plurality of isolated circles or viasaround a perimeter of interconnect site or bump formation area 155. Theopenings 154 have a similar cross-sectional view as FIG. 4e and exposeencapsulant 144 outside a footprint of semiconductor die 124. Theopenings 154 can be distributed near the edge, e.g., 40 μm clearance, ofinterconnect site 155.

In FIG. 4h , an electrically conductive layer 156 is conformally appliedover insulating layer 146, encapsulant 144, and the exposed contact pads132 using a patterning and metal deposition process such as PVD, CVD,sputtering, electrolytic plating, and electroless plating. Conductivelayer 156 can be one or more layers of Al, Cu, Sn, Ni, Au, Ag, or othersuitable electrically conductive material. Conductive layer 156 followsthe contour of insulating layer 146, including into ring-shaped opening148 on encapsulant 144. More specifically, conductive layer 156 isformed directly on encapsulant 144 within ring-shaped opening 148.Likewise, conductive layer 156 is formed directly on encapsulant 144within openings 152 and 154 of FIGS. 4f and 4g . Conductive layer 156can be a seed layer or adhesion layer containing Ti/Cu, TiW/Cu, Ta/Cu,Cr/Cu, Ni, NiV, Au, or Al.

In FIG. 4i , an electrically conductive layer or RDL 158 is formed overconductive layer 156 using a patterning and metal deposition processsuch as PVD, CVD, sputtering, electrolytic plating, and electrolessplating. Conductive layer 158 can be one or more layers of Al, Cu, Sn,Ni, Au, Ag, or other suitable electrically conductive material. Theportions of conductive layer 158 can be electrically common orelectrically isolated depending on the design and function ofsemiconductor die 124.

In FIG. 4j , an insulating or passivation layer 160 is formed overinsulating layer 146 and conductive layer 158 using PVD, CVD, screenprinting, spin coating, spray coating, sintering or thermal oxidation.The insulating layer 160 contains one or more layers of SiO2, Si3N4,SiON, Ta2O5, Al2O3, or other material having similar insulating andstructural properties. A portion of insulating layer 160 is removed toexpose conductive layer 158 over interconnect site or bump formationarea 150.

In FIG. 4k , an electrically conductive bump material is deposited overinterconnect site 150 and the exposed conductive layer 158 using anevaporation, electrolytic plating, electroless plating, ball drop, orscreen printing process. The bump material can be Al, Sn, Ni, Au, Ag,Pb, Bi, Cu, solder, and combinations thereof, with an optional fluxsolution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded toconductive layer 158 using a suitable attachment or bonding process. Inone embodiment, the bump material is reflowed by heating the materialabove its melting point to form spherical balls or bumps 164. In someapplications, bumps 164 are reflowed a second time to improve electricalcontact to conductive layer 158. The bumps can also be compressionbonded to conductive layer 158. Bumps 164 represent one type ofinterconnect structure that can be formed over conductive layer 158. Theinterconnect structure can also use stud bump, micro bump, or otherelectrical interconnect.

In Fo-WLCSP 166, the portion of conductive layer 156 (and RDL 158)formed directly on encapsulant 144 within ring-shaped opening 148outside a footprint of semiconductor die 124 provides enhanced adhesionand reliability for anchoring bumps 164. Likewise, conductive layer 156(and RDL 158) can be formed directly on encapsulant 144 within openings152 and 154 for enhanced adhesion and reliability. A portion ofconductive layer 156 (and RDL 158) is disposed directly on insulatinglayer 146 outside a footprint of semiconductor die 124 for stress reliefand buffering of encapsulant 144 and to balance the stress on thesemiconductor die.

In another embodiment, continuing with the structure described up toFIG. 4c , an insulating or passivation layer 168 is formed oversemiconductor die 124 and encapsulant 144 using PVD, CVD, screenprinting, spin coating, spray coating, sintering or thermal oxidation,as shown in FIG. 5a . The insulating layer 168 contains one or morelayers of SiO2, Si3N4, SiON, Ta2O5, Al2O3, or other material havingsimilar insulating and structural properties. A portion of insulatinglayer 168 is removed by an etching process to form openings or vias 170and expose contact pads 132 and encapsulant 144.

FIG. 5b shows a plan view of insulating layer 168 and openings 170formed as a plurality of isolated circles or vias uniformly distributedacross interconnect site or bump formation area 172. The openings 154can be distributed near the edge, e.g., 40 μm clearance, and within aninterior (central) region of interconnect site 172. The openings 170expose encapsulant 144 outside a footprint of semiconductor die 124.

In FIG. 5c , an electrically conductive layer 174 is conformally appliedover insulating layer 146, encapsulant 144, and the exposed contact pads132 using a patterning and metal deposition process such as PVD, CVD,sputtering, electrolytic plating, and electroless plating. Conductivelayer 174 can be one or more layers of Al, Cu, Sn, Ni, Au, Ag, or othersuitable electrically conductive material. Conductive layer 174 followsthe contour of insulating layer 146, including into openings 170 onencapsulant 144. More specifically, conductive layer 174 is formeddirectly on encapsulant 144 within openings 170. Conductive layer 170can be a seed layer or adhesion layer containing Ti/Cu, TiW/Cu, Ta/Cu,Cr/Cu, Ni, NiV, Au, or Al.

An electrically conductive layer or RDL 176 is formed over conductivelayer 174 using a patterning and metal deposition process such as PVD,CVD, sputtering, electrolytic plating, and electroless plating.Conductive layer 176 can be one or more layers of Al, Cu, Sn, Ni, Au,Ag, or other suitable electrically conductive material. The portions ofconductive layer 176 can be electrically common or electrically isolateddepending on the design and function of semiconductor die 124.

In FIG. 5d , an insulating or passivation layer 178 is formed overinsulating layer 146 and conductive layer 176 using PVD, CVD, screenprinting, spin coating, spray coating, sintering or thermal oxidation.The insulating layer 178 contains one or more layers of SiO2, Si3N4,SiON, Ta2O5, Al2O3, or other material having similar insulating andstructural properties. A portion of insulating layer 178 is removed toexpose conductive layer 176 over interconnect site or bump formationarea 172.

In FIG. 5e , an electrically conductive bump material is deposited overinterconnect site 172 and the exposed conductive layer 176 using anevaporation, electrolytic plating, electroless plating, ball drop, orscreen printing process. The bump material can be Al, Sn, Ni, Au, Ag,Pb, Bi, Cu, solder, and combinations thereof, with an optional fluxsolution. For example, the bump material can be eutectic Sn/Pb,high-lead solder, or lead-free solder. The bump material is bonded toconductive layer 176 using a suitable attachment or bonding process. Inone embodiment, the bump material is reflowed by heating the materialabove its melting point to form spherical balls or bumps 180. In someapplications, bumps 180 are reflowed a second time to improve electricalcontact to conductive layer 176. The bumps can also be compressionbonded to conductive layer 176. Bumps 180 represent one type ofinterconnect structure that can be formed over conductive layer 176. Theinterconnect structure can also use stud bump, micro bump, or otherelectrical interconnect.

In Fo-WLCSP 182, the portion of conductive layer 174 (and RDL 176)formed directly on encapsulant 144 within openings 170 outside afootprint of semiconductor die 124 provides enhanced adhesion andreliability for anchoring bumps 180. A portion of conductive layer 174(and RDL 176) is disposed directly on insulating layer 146 outside afootprint of semiconductor die 124 for stress relief and buffering ofencapsulant 144 and to balance the stress on the semiconductor die.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

What is claimed:
 1. A method of making a semiconductor device,comprising: providing a semiconductor die including a first conductivelayer formed on a surface of the semiconductor die; forming a firstinsulating layer over the surface of the semiconductor die; depositingan encapsulant over the semiconductor die with a surface of theencapsulant coplanar with the surface of the semiconductor die; forminga second insulating layer over the surface of the encapsulant and overthe first insulating layer and extending to contact the first conductivelayer; forming an interconnect site outside a footprint of thesemiconductor die by removing a portion of the second insulating layerwithin the interconnect site over the encapsulant to form an openingextending to the surface of the encapsulant while leaving a portion ofthe second insulating layer in an interior region of the interconnectsite; and forming a second conductive layer over the interconnect siteto contact the portion of the second insulating layer and extending intothe opening to contact the surface of the encapsulant.
 2. The method ofclaim 1, further including forming a bump over the second conductivelayer.
 3. The method of claim 1, wherein the opening includes a ringshape around the portion of the second insulating layer in the interiorregion of the interconnect site.
 4. The method of claim 1, wherein theopening includes a plurality of vias disposed around a perimeter of theinterconnect site.
 5. The method of claim 1, further including forming athird conductive layer over the interconnect site.
 6. The method ofclaim 1, further including forming a third insulating layer over thesecond insulating layer.
 7. A method of making a semiconductor device,comprising: providing a semiconductor die; depositing an encapsulantover the semiconductor die with a surface of the encapsulant coplanarwith a surface of the semiconductor die; forming a first insulatinglayer over the surface of the encapsulant; forming an interconnect siteoutside a footprint of the semiconductor die by removing a portion ofthe first insulating layer within the interconnect site over theencapsulant to form an opening extending to the surface of theencapsulant while leaving a portion of the first insulating layer in aninterior region of the interconnect site; and forming a first conductivelayer over the interconnect site to contact the portion of the firstinsulating layer and extending into the opening to contact the surfaceof the encapsulant.
 8. The method of claim 7, further including formingan interconnect structure over the first conductive layer.
 9. The methodof claim 8, wherein the interconnect structure includes a bump.
 10. Themethod of claim 7, wherein the opening includes a ring shape around theportion of the second insulating layer in the interior region of theinterconnect site.
 11. The method of claim 7, wherein the openingincludes a plurality of vias disposed around a perimeter of theinterconnect site.
 12. The method of claim 7, further including forminga second insulating layer over the surface of the semiconductor die,wherein the first insulating layer extends over the second insulatinglayer to contact a second conductive layer on the semiconductor die. 13.The method of claim 7, further including forming a second insulatinglayer over the interconnect site.
 14. A method of making a semiconductordevice, comprising: providing a semiconductor die; depositing anencapsulant over the semiconductor die; forming a first insulating layerover a surface of the encapsulant; forming an interconnect site outsidea footprint of the semiconductor die by removing a portion of the firstinsulating layer within the interconnect site over the encapsulant toform an opening extending to the surface of the encapsulant whileleaving a portion of the first insulating layer in an interior region ofthe interconnect site; and forming a first conductive layer over theinterconnect site to contact the portion of the first insulating layerand extending into the opening to contact the surface of theencapsulant.
 15. The method of claim 14, further including forming aninterconnect structure over the first conductive layer.
 16. The methodof claim 14, wherein the opening includes a ring shape around theportion of the second insulating layer in the interior region of theinterconnect site.
 17. The method of claim 14, wherein the openingincludes a plurality of vias disposed around a perimeter of theinterconnect site.
 18. The method of claim 14, further including forminga second conductive layer over the interconnect site.
 19. The method ofclaim 14, further including forming a second insulating layer over thesemiconductor die, wherein the first insulating layer extends over thesecond insulating layer to contact a second conductive layer on thesemiconductor die.
 20. A semiconductor device, comprising: asemiconductor die; an encapsulant deposited over the semiconductor die;a first insulating layer formed over a surface of the encapsulant; aninterconnect site located outside a footprint of the semiconductor die,wherein the interconnect structures includes an opening in the firstinsulating layer and a portion of the first insulating layer in aninterior region of the interconnect site; a first conductive layerformed over the interconnect site to contact the portion of the firstinsulating layer and extending into the opening to contact the surfaceof the encapsulant; and forming a second insulating layer over thesurface of the semiconductor die, wherein the first insulating layerextends over the second insulating layer to contact a second conductivelayer on the semiconductor die.
 21. The semiconductor device of claim20, further including forming an interconnect structure over the firstconductive layer.
 22. The semiconductor device of claim 20, wherein theopening includes a ring shape around the portion of the secondinsulating layer in the interior region of the interconnect site. 23.The semiconductor device of claim 20, wherein the opening includes aplurality of vias disposed around a perimeter of the interconnect site.24. The semiconductor device of claim 20, further including a secondconductive layer formed over the interconnect site.